Thermally toughened insulator



Patented Apr. 8, 1947 THERMALLY TOUGHENED INSULATOR Minot K. Holmes, Muncie, Ind., and Jesse B.

Plummer, Toledo, Ohio, asslgnors to Owens- Illinois Glass Company, a corporation of Ohio Application September 14, 1944, Serial No. 554,036

- 5 Claims. 1

Guzinvention relates to glass insulators and methods for thermally treating them. A thermally toughened glass article having a hardened surface layer under compression enveloping an interior body or mass under tension, is many times stronger than a similar well annealed article. However, when such a thermally toughcued glass article breaks, it fractures into liter ally thousands of small pieces. A glass insulator for line wires or cables, when thermally toughened in accordance with conventional nods, is much stronger and more resistant to l t than an annealed insulator, but in the event breakage zit-would shatter into many and fail to support the line. This is one rests-n why glass insulators have not come into more itensive use on power lines.

insulator which is so designed and them t portion, sufficient to cause breakage, the are confined. to area of the skirt while body of the insulator remains intact and continues to hold the l ne wire or cable in position. In accordance with our invention the body of the insulator is made so strong as to be practicaily unbreakable.

A "urther object of our invention is to provide a thermally treated surface hardened insulator with the surface portion under compression and the interior portion under tension. designed and treated in such a manner that when the skirt portion is broken by impact or thermal shock, the body of the insulator is protected'and remains intact.

Other obj ects of the invention will appear hereinafter.

Referring to the accompanying drawings which illustrate an insulator and means for thermally treating the same:

Fig. i is a part seotional elevation of the insulator before being subjected to thermal treatment.

Fig. 2 is a plan view of the same.

Fig. 3 is a part-sectional elevation of the insulator and means for thermally treating the same.

Fig. 4 is a view similar to Fig. 3 showing a modification.

The insulator which is molded in a single piece, comprises a body portion 5 and a depending skirt 5 which merges into or is united with the body 5 by a neck portion 1 at an intermediate point between the upper and lower ends of the body 5. The insulator is formed with the usual central opening 8 provided with screw threads 9 for atect of the present invention is to provide treated that in the event of impact on the tachment to the pin on which it is mounted when in use. An inner skirt or petticoat l depends from the body of the insulator and is spaced inwardly from the skirt 6, thereby providing an annular space H between said skirts.

Apparatus for thermally treating the insulator comprises a table or support l2 which may be rotated by a power driven roll 43. The table i2 is formed with a central opening l4 and provided with an annular series of pins iii to support the insulator over said opening. A blower It comprises a vertical air pipe which projects upwardly within the opening a, centrally thereoi. is provi d with a multiplicity of jet openl'i as through the "walls of the pipe against the la i as from 7 suitable source pipe it. A pi e ,open 'tstree 1 out pipe it; and projects up -e annular space slower for blow i Th jet oi air from the it toward the l of the skirt 3.

The method of thermally treating 511.19 later is as follows:

When the insulator removed from the iorm= ins; machine or mold and while at a high tomperature, is first stabilized for approximately ten minutes by placing it in a iurnace in which a uniform temperature of about li5l is maintained. This temperature, however. may he varied between about woo and we F. or higher temperatures, the most suitable temperature de-' pending on variable factors such as the glass composition, the length of time within the furnace, the design of the insulator, and the intensity of the treatment desired.

When the insulatoris removed from the furuses it is placed on the rotating table 12 while air under pressure is supplied to the slower IS. The air jets from the openings ll are thus directed against the inner surface of the insulator while at the same time the branch pipe it blows air into the space H and directs it more or less forceably against the inner surface oi the neck portion 7.

By this treatment the entire surface portions of the insulator are chilled and tempered or hardened. We have found that in practice it is unnecessary to provide any special blowing means for chilling the exterior surface of the insulator, asthe rapid rotation thereof in the enveloping air results in the. desired rapid chilling and tempering 0! said surface. The chilled surface portion or layer 20, indicated by shade lines, extends to a greater or lesser depth. When the insulator as a whole is cooled, the surface layer 20 thereof is under compression while the interior portion of the insulator body is placed under tension. The skirt 6, as well as the body 5, comprises a surface portion or layer which is chilled and hardened and an interior portion which is under tension. The inner petticoat I being comparatively thin, is chilled and hardened throughout.

The neck portion 1, as indicated by the heavy shading, is chilled and hardened throughout its entire thickness. This localized chilling of the neck 1 results from directing the Jet from the branch pipe i8 against this portion and may be augmented by an air blast from an exterior blow- .pipe 2| (Fig. 4) 'also directed toward the neck portion 1. Also the walls at this portion may be made comparatively thin as shown at 'i in Fig. 4 by widening the upper portion of the recess II or other change in the contour such as a shallow groove in the skirt where it joins the body of the insulator.

We have found that by thermally treating the insulator in the manner above described, any impact or shock applied to the skirt and resulting in breakage thereof, confines such breakage to the skirt portion of the insulator, as the hardened portion 1 provides a protecting wall between the skirt and the interior body portion which is under tension.

The present method of thermally treating the insulator results in completely encasing the in terior of the insulating body 5 in an outer hardened casing or shell 20 under compression while the skirt 6 also includes an interior mass under tension encased in an outer hardened shell under compression. The interior tensioned masses comprised'in said body and skirt respectively are separated by the zone or neck i of hardened material under compression. The insulator thus treated has great strength and is superior both to an annealed insulator and one in which the body of the insulator is hardened throughout. The outer skirt 6, which in service receives most of the blows that tend to break an insulator, is also resistant to shock by impact but when it is broken, the body of the insulator is completely protected against shattering by the tempered neck portion 1 which prevents the breakage from extending to the tension area of the insulator body.

Modifications may be resorted to within the spirit and scope of our invention.

We claim:

1. An insulator comprising a body and an annular skirt integral therewith, said body and skirt having surface layers hardened and under compression and interior portions under tension, the neck portion of glass forming the juncture between the skirt and body being hardened throughout and thereby separating said tensioned glass into separate bodies.

2. An insulator comprising a body and an annular skirt integral therewith, said body and skirt having surface layers hardened and under compression and interior portions under tension. the neck portion of glass forming the juncture between the skirt and body being hardened throughout and thereby separating said tensioned glass into separate bodies, said neck portion being of substantially less wall thickness than the body of said skirt.

3. A glass insulator comprising a body having a surface layer thereof hardened and under compression, the interior mass of glass in said body being under tension. an annular skirt integral with said body, said skirt comprising a hardened surface layer of glass under compression and an interior mass of glass under tension, said skirt being united to said body by a neck portion, the latter being hardened throughout and separating said interior masses.

4. A glass insulator comprising a body, said insulator having a central opening extending upwardly from the bottom thereof into said body, said insulator including an inner skirt depending from said body and defining the lower portion of said opening and an outer skirt surrounding said inner skirt and dire:tly united to said body above the inner skirt, said body and outer skirt each having a surface layer thereof hardened and under compression and an interior mass under tension, said interior masses being separated by a hardened portion of said outer skirt.

5. A glass insulator comprising a body, said insulator having a central opening extending upwardly from the bottom thereof into said body, said insulator including an inner skirt depending from said body and defining the lower portion of said opening and an outer skirt surrounding said inner skirt and directly united to said body above the inner skirt, said body and outer skirt each having a surface layer thereof hardened and imder compression and an interior mass under tension, said inner skirt being hardened throughout and said outer skirt comprising an annular portion hardened throughout and separating said interior masses.

MINUI K. HOLMES. JESSE H. PLUMLIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,198,734 Littleton Apr. 30, 1940 2,344,630 Mylchreest Mar. 21, 1944 2,254,227 Lewis Sept. 2, 1941 2,157,100 Rowland May 9, 1939 2,097,073 Long Oct. 26,193! 2,287,976 Croskey et al June 30, 1942 2,081,508 Shaver May 25, 1937 

